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基于涡模型的大跨悬挑结构附面层吹气控制研究

发布时间:2018-06-18 00:40

  本文选题:大跨悬挑结构 + 数值模拟 ; 参考:《哈尔滨工业大学》2017年硕士论文


【摘要】:随着建筑科技的发展,大跨悬挑结构被广泛应用于生活中的方方面面,尤其以体育场最为常见。当前,在计算大跨悬挑结构屋面风压时,由于常用的基于拟定常假定的风压计算方法失效,大跨悬挑结构屋面风压计算的简便方法只有基于风洞试验的经验参数法,但该方法对外形多变的结构形式适用性较差,对于结构的抗风设计极为不便;同时,作为典型柔性结构,大跨悬挑结构自振频率低,对风荷载极为敏感,其风振响应不容忽视。针对以上问题,本文从机理上分析了屋面风压产生的原因,引入涡模型为纽带,将来流风特性与屋面风压分布特性相联系,提出相应的屋面风压理论模型,并基于此,提出新的吹气控制方式以及不同工况下的最佳控制方案。通过研究来流风特性与涡形态特性之间的关系,建立了大跨悬挑结构表面涡的流动速度的理论模型。采用CFD数值仿真模拟大跨悬挑结构的实际绕流情况,确定影响屋面风压分布的关键参数,围绕大跨悬挑结构屋面涡外形特性、分布特性和速度剖面特性等展开研究。基于数值仿真结果,提出了“涡心漂移”假定,并基于该假定,揭示屋面各处涡速度剖面具有“相似性”,进而确定了来流风特性与涡特性之间的关系,建立了适合大跨悬挑结构屋面各处的涡流动速度模型。开展涡形态与屋面风压特性关系的研究,提出了基于涡流动模型的大跨悬挑结构屋面风压计算方法。根据大跨悬挑结构屋面涡形态与风压变化特性的不同将屋面分为前缘分离区、旋涡区和旋涡分离区三个区域。通过涡心距屋面高度h变量的引入和对现有风压模型的曲率半径进行修正,解决了大跨悬挑结构旋涡下部无极值点、势流区速度不随轴向变化、涡心距离屋面较近的特异性问题。基于该修正的风压模型,研究了大跨悬挑结构各外形参数(屋盖倾角、下部看台通风率、长宽比、高跨比)耦合作用的影响,提出外形影响系数进行量化分析。基于前文理论研究,提出了附面层吹气控制方法。通过附面层吹气,控制屋面涡的形态以减小屋面风压。采用CFD数值仿真的方法验证了该控制方法的有效性,发现在前缘分离区、旋涡区和旋涡分离区三个区域的吹气控制效果不同。研究了三个区域的吹气速度对大跨悬挑结构屋面风压极值的影响以及布置位置对消涡效果的影响,提出最佳控制方案。充分考虑外部风环境因素对最佳控制方案的影响,提出相应的改进策略,确保附面层吹气控制具有较为广泛的工程应用范围。
[Abstract]:With the development of architectural science and technology, long-span cantilever structures are widely used in many aspects of life, especially in stadiums. At present, in calculating the roof wind pressure of long-span cantilever structure, due to the failure of the usual calculation method based on the usually assumed wind pressure, the simple method for calculating the wind pressure of long-span cantilever structure roof is based on the empirical parameter method of wind tunnel test. However, this method is not suitable for the structural form with changeable shape, and is very inconvenient for the wind-resistant design of the structure. As a typical flexible structure, the long-span cantilever structure has low natural vibration frequency and is extremely sensitive to wind load, and its wind-induced response can not be ignored. In view of the above problems, this paper analyzes the causes of roof wind pressure from the mechanism, introduces the vortex model as a link, the future flow wind characteristics and roof wind pressure distribution characteristics are related to the corresponding roof wind pressure theoretical model, and based on this, A new blowing control method and the optimal control scheme under different operating conditions are proposed. A theoretical model of vortex flow velocity on long-span cantilever structure is established by studying the relationship between wind characteristics and vortex-shape characteristics. CFD numerical simulation is used to simulate the actual flow around the long-span cantilever structure, and the key parameters affecting the roof wind pressure distribution are determined. The profile characteristics, distribution characteristics and velocity profile characteristics of the roof vortex of the long-span cantilever structure are studied. Based on the numerical simulation results, the hypothesis of "vortex drift" is proposed. Based on this assumption, the "similarity" of vortex velocity profiles around the roof is revealed, and the relationship between the characteristics of the incoming wind and the vortex characteristics is determined. The eddy current velocity model for long span cantilever roof is established. In this paper, the relationship between vortex shape and roof wind pressure characteristics is studied, and a calculation method for roof wind pressure of long-span cantilever structure based on eddy current model is proposed. According to the different characteristics of roof vorticity and wind pressure of long-span cantilever structure, the roof is divided into three regions: front edge separation region, vortex region and vortex separation region. By introducing the h variable from the roof height of the vortex center and modifying the curvature radius of the existing wind pressure model, it is solved that there is no pole value point in the vortex lower part of the cantilever structure, and the velocity of the potential flow zone does not change with the axial direction. The specificity of the vortex center close to the roof. Based on the modified wind pressure model, the influence of various shape parameters (roof inclination, lower stand ventilation ratio, aspect ratio and height span ratio) on the coupling action of long-span cantilever structure is studied. Based on the previous theoretical research, a boundary layer blowing control method is proposed. The shape of roof vortex is controlled by boundary layer blowing to reduce roof wind pressure. The effectiveness of the control method is verified by CFD numerical simulation. It is found that the control effect is different in the leading edge separation region, the vortex region and the vortex separation region. The influence of blowing velocity in three regions on the wind pressure extremum of roof of long-span cantilever structure and the effect of placement position on vortex suppression are studied. The optimal control scheme is put forward. Considering the influence of the external wind environment factors on the optimal control scheme, the corresponding improvement strategies are put forward to ensure that the boundary layer blowing control has a relatively wide range of engineering applications.
【学位授予单位】:哈尔滨工业大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TU312.1

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